A Comparative Study Of Different Doses Of ¹³¹I Remnant Ablation In Patients After Thyroidectomy For Intermediate Risk Differentiated Thyroid Cancer

Objectives:Radioiodine(¹³¹I)remnant ablation therapy for post-thyroidectomy of differentiated thyroid cancer（DTC）is the main method to remove residual thyroid tissue which can not be completely removed by the operation.The purpose of this paper is to investigate the therapeutic effect of different doses of ¹³¹I in the removal of residual thyroid gland,and the factors of side effects.So as to explore whether it can reduce the dose of thyroid remnant ablation and reduce the incidence of adverse reactions.Methods:Retrospectively collected and analyzed the DTC patients who accepted ¹³¹I thyroid remnant ablation therapy for the first time after thyroidectomy in the First Affiliated Hospital of China Medical University from September 2017 to September2018.Thyroid static imaging was performed before the therapy.The results were analyzed by visual analysis method.According to the imaging results,the patients with positive imaging were regarded as the residual thyroid group,while the patients with negative imaging were regarded as the non-residual thyroid group.According to the different treatment doses,the residual thyroid group and the non-residual thyroid group were divided into small dose group,medium dose group and large dose group.Following up for 3-12 months,according to the therapeutic response assessment system proposed by the ¹³¹I Guidelines for Differentiated Thyroid Carcinoma（2014edition）of the Nuclear Medicine Branch of the Chinese Medical Association,the therapeutic effect of the patients was assessed into thyroid removal failure,thyroid removal success,complete remission of the tumor,and the side effects after treatment were divided into:no side effects,temporary response,persistent response.Univariate analysis method was made on the difference of therapeutic effect between the residual thyroid group and the non-residual thyroid group,as well as the possible factors affecting the occurrence of side effects(age,gender,symptoms of salivary gland injury before treatment,whether there was residual thyroid before treatment,¹³¹I dosage).Then these factors with statistical differences were analyzed by multivariate analysis method.Wilcoxon rank sum test and Kruskal-Wallis_H test were used for univariate analysis,and Binary Logistic regression analysis was used for multivariate analysis.P<0.05 means statistical significance.Results:A total of 215 patients with complete data were collected,including 61males（28.4%）and 154 females（71.6%）.The average age was 44.81+11.57 years.Before treatment,135 cases（62.8%）had residual thyroid tissue,including 72 cases of low dose,39 cases of medium dose and 24 cases of high dose;80 cases（37.2%）had no residual thyroid tissue,including 15 cases of low dose,21 cases of medium dose and 44 cases of high dose.¹³¹I remnant ablation treatment results:17 cases（7.9%）failed thyroid removal,86 cases（40.0%）only succeeded thyroid removal,112 cases（52.1%）had complete remission of tumors.After ¹³¹I remnant ablation,59 cases（27.4%）had no side effects,103 cases（47.9%）had temporary response and 53 cases（24.7%）had persistent response.Univariate analysis showed that there was no significant difference in the therapeutic effect between the residual thyroid group and the non-residual thyroid group at different doses,and there was no significant difference in the therapeutic effect between the residual thyroid group and the non-residual thyroid group（P>0.05）.There were significant differences in ¹³¹I treatment dose and residual thyroid tissue among different side effects（Z=6.775,-2.311,P=0.034,0.021）,while age,gender and symptoms of salivary gland injury before treatment were not significant differences（all P>0.05）.Multivariate analysis revealed that ¹³¹I treatment dose（OR=2.305,95%CI:1.466-3.625,P<0.05）and residual thyroid tissue（OR=4.302,95%CI:2.020-9.162,P<0.05）were independent risk factors for side effects;¹³¹I treatment dose（OR=1.561,95%CI:1.034-2.356,P=0.034）was an independent factor for long-term side effects.Conclusions:After excluding the residual thyroid factor,the ¹³¹I treatment dose is not the influencing factor of radioiodine remnant ablation treatment,and the residual thyroid can not affect the result of radioiodine remnant ablation.¹³¹I treatment dose is an independent influencing factor for different side effects.The larger the dose,the more likely side effects will occur,and the more likely persistent response will occur.The residual thyroid is only an independent influencing factor for the occurrence of side effects,and patients with residual thyroid are more likely to have temporary response,but it can not affect the occurrence of persistent response.